Rolling mills



p 1958 w. c. F. HESSENBERG 2,851,911

ROLLING MILLS Filed Jan. 25. 1955 United States Patent F ROLLING MILLSillttilired Cecil 'Frede'rick liessenbergnsBi-omleyn England,

.assignonto-The lBritish-rlronrfia Steel :Research EAssocia- L tion,London,-E ngland ApplicationJanuaryflS, 1955', SerialNo. 483,910

;,Glaims: priori y, application. Great Britain ,-January;26, 1954 .This:invention relates .to rolling.mills,,particularly,,tor steel. Rollingmills may be :so. arranged. that the, rolled material .is ,passing;throngh. a number .of.,.individual. roll standstat thesame time. ,Thecontinuous ..st rip,.,mill-.in .which the strip: passes ,simultaneouslythrough several astandssarranged in tandem is a..well,known example. Oneof the objects of continuous rolling isnto aproduce long lengths of.materialhaving a desired-:cross-section .which varies.v as .little :as.possible, ,from zone, end ;to ,the other. -,.In a. .tandem strip,.mill, changes;in...thickness,may occur as the. resultof disturbancesin.one..or,-more-.of .the. roll ;s,tands... and Lit ;.is .desirable;that .these..should .be. corrected ,before Ithe materiahissues 1mmhegdast stand. A Obiechof .thisinvention is .to ,provide, a, methodfona'chievingithis.

Itaisua. characteristic. of- .continuous mills ,that, .pnless .j the[material ,is;,allowed to. .aecurnulatebetween ,thestands or issubjected to increasingandfinally destructiyedensile stresses,..therate;. in volume, unitsper...second..at, which .materiaL leaves. onestandmust. equal .therate .at .which .it. enters v.the next. It.is...a1so.we1l, known t hat',in..the rolling. ofmetals;theirdensityis.notrappreciablysafiected by the. deformation.they, receive. ,.-I't is. therefore, possi- ,ble .to, ;state.j.thatinna continuous.,;mill twherethe material ne,ither, accumulates .nor. issubjectedto in reasing tension .between ..the ,stands,,;the, volume,,ofimaterial :passing: any point v ina giventimeis ithehsamemfor, all.points.,throughout'the system. In the special case of a widestriprrnill where the width of the strip is not afiected by rolling, thethickness ofsthe strip multipliedbyatthenspeed ofthe strip willyieldathesameeproduct at,,. any point. product is the output of'themill.

The present invention employs the above -features-- to provide apparatus-or a measuring the issuing thickness c of strip from a -rolling milland for controlling-"the; mill tormaintaina strip-thickness ata----'de"sired value. fThus, aaccording tothe-present invention?in amethodof measur- Ling the thickness-ofl str-ipleaving a=rolling milhthe-outgoing thicknessisderived from measurement of the speed sandthickness of thestrip prior -to-=- passage ';out-of :the crnill randof-ithespeed-of the stripdeaW-ing the-= mill. "--For a multi-stand mill,i, the ,sp.eed-;.and;;thickness is measured .between any two adjacentstands. so that the,,output can "be' derived; the-outputis--'then'compounded with the speed of the strip leaving the mill to give anindication of the issuing strip thickness.

The invention includes apparatus for maintaining at the desired valuethe thickness of wide strip leaving a multi-stand rolling millcomprising means for producing signals in accordance with the speed (vand the thickness (h of the strip between two adjacent .stands of themill, means for producing a signal in accordance with the speed of thestrip (v leaving the mill, means for compounding the said signals toproduce a resultant signal, representing the issuing thickness, inaccordance with Patented Sept. 16, 1958 and means controlled by theresultant signal for maintaining the issuing thickness at thedesiredvalue.

The invention will be more readily understood by. way of example fromthe following description of a continuous multi-stand steel rollingmill,reference being made to the accompanying drawing which is a schematicrepresentation of the mill.

;In the drawing, the rolls of the stands of the mill are indicated at12a, 12b, 12c etc., it being understood that. :the mill may have as manystands as may be desirable. Between any two adjacent stands, there arelocated a micrometer 13 which gives an electrical signal on the outputlines 14 in accordance with the thickness of the strip 15 between thosestands, and a device for giving an electric signal proportional to the.linear. speed Jofia'the, 'stripas; itpasses between the-stands. This.device consists, of a discjl6' mounted on the rotor-ofa tachometricgenerator17, the arrangement being such that theplane 'of'the disc 16 isaligned with the direction of motion a-ofthe;strip15 and ,thediscrotatesatthe ,same peripheral This speed as the strip. The micrometer13and thedevice .16, 17 are shown between the last twostands of the mill,but it will be understood that they maybe located between any two-otherstands.

7 A second device for measuring the speed of the strip .is located. atthe issuing @side of ,the. :last roller stand 12a. This device issimilar to the device 16, 17 andcomprises a disc .18 in. frictionalcontact-with the strip and carried onthe motor of a tachometricgenerator, 19.

1 .The;millzis provided--with .the customary, reeling rdrum .ztlforqthestrip, the reeler motor 211anda drivingmotor .22 andscrew-down motor 23foreach'ofthe rollerstands; .-the driving motor 22 drives therolls,-whereas the screw- *-down. motor,23 causesadjustment-in.the-initialsetting of the work rolls 12 in relation to oneanother.

The output. of generator 1 9.; appearing at ,lines .24 ,is appliedacross an arcuate potentiometer 25. The signal appearing betweentheslider 26 ofthe potentiometer and tone endof the potentiometer isapplied inseriesopposi- .tiontolhe output from generator,17 to. theinput of..a high gain amplifier 27, the output from which is .connectedto a light motor 28. The rotor shaftof motor .28 carries the slider 26of potentiometer 25 and also .the.slider- 29 of a second arcuatepotentiometer 30. The ;electric 1signal appearing on the output lines14-of micronl ter, 13 is applied across potentiometer. 30,and, thesignalappearing on the slider 29,and;one end ,:of'the potentiometer isproportional to the outgoing thickness .of..the..s trip and anindication of that thickness can :be

givenby connecting the twopoints to a imeter 31.

Alternatively, a signal may be derived proportional to thei.de,viationof the issuingthickness ,froma, given value ,by connecting slider 29 andone. side of .the po- .tentiometer 30 ,in series opposition, to. a.source. ofvolt- ,age indicated in the vdrawing as a battery-32,connected acrossthe. potentiometer 33. .The sliderarm29 .is con-,anected. to..,the.,s lider 34 of potentiometer .33 and the difierencevoltage 1 appears .onslines 35.

In order to provide an automatic control system for maintaining theissuing thickness of the strip substantially at a given value determinedby the setting of the potentiometer 33, the signal appearing on lines 35may be applied to the reeler motor 21, as shown, or alternatively to anyof the screw-down motors 23 of the roll stands or to any of the drivemotors 22, as indicated in chain line.

The operation of the system is as follows. If the speed and thickness ofthe strip between stands 12a and 12b are v I1 and the speed andthickness of the strip, as it leaves the mill, are v and k then thevoltage applied across potentiometer 25 is V proportional to v and thevoltage appearing between slider arm 26 and one end of the potentiometeris kV where k is determined by the position of the slider on thepotentiometer. The voltage applied the input of amplifier 27 istherefore proportional to (V kV where V is proportional to v as the gainof the amplifier 27 is large the angular position of the rotor shaft ofmotor 28 will be since at balance the input to the amplifier will bevery nearly zero. Thus, as the voltage applied across potentiometer 30is proportional to h the signal appearing at the slider 29 and one endof the potentiometer 30 is proportional to and because the output forwide strip is constant along the whole length of the strip and thereforeh v =h v this signal is proportional to 12 the issuing thickness of thestrip and the meter 31 will indicate that thickness.

When used, the potentiometer 33 applies a constant voltage h inopposition to the voltage from potentiometer 30 and the signal appearingat output lines 35 is therefore h h, the deviation of the thickness froma given value.

When this voltage is applied to control any of motors 21, 22 or 23, therolling mill will operate to maintain the output signal on lines 35 zeroor, in other words, the issuing thickness of the strip at the desiredvalue h, determined by the position of the slider 34.

As will be appreciated, the system illustrated in the accompanyingdrawing enables the thickness or gauge of the strip leaving the mill tobe measured indirectly with the attendant advantage that the stripthickness is measured as it leaves the last roll stand and not at somedistance from that stand. This advantage is of particular value when thesystem is used for automatic control of the mill as it enablesirregularities in the thickness to be compensated immediately instead ofafter a time lag.

In another embodiment, the micrometer and the two speedometers areemployed as before, but in this case percentage variations are measured.The signals from the micrometer and speedometer located between thestands are compounded to give a resultant signal equal to the output (vxh From this resultant signal is obtained a signal proportional to thepercentage variation of the output from a given value, the given valuecorresponding to a desired thickness. Similarly, the signal from thespeedometer measuring the speed of the issuing strip is modified to givea signal proportional to the percentage variation in the issuing stripthickness from the given value, again corresponding to the desiredthickness. The two percentage signals are applied in series oppositionto give a difference signal proportional to the percentage variation ofthe issuing thickness of the strip from the desired value. This signalcan be applied to the reeling motor or to the screw-down or drivingmotors of the stands to compensate automatically for variations in thethickness and to maintain that variation zero.

As a result of the adjustments in accordance with the percentagevariation signal, there will occur changes in the tensions in the stripbetween the stands, which will bring the Whole system into a newequilibrium. Changes in the thickness arising anywhere in the mill willbe ofiset by the efiects of these changes in tension on the stripthickness in such a way that there will be no resultant change in thethickness of the strip as it leaves the final stand.

What is claimed, is:

1. In a rolling mill having a motor operated final stand and at leastone motor operated preliminary stand, manually adjustable means forcontrolling the thickness of the strip issuing from said final stand,first variable signal generating means responsive to the velocity of apartially finished strip supplied to said final stand, second variablesignal generating means responsive to the thickness of said stripsupplied to said final stand, third variable signal generating meansresponsive to the velocity of the strip issuing from said final stand,and a signal correlating means responsive to the setting of saidmanually adjustable means and all of said signal generating means, saidcorrelating means varying the speed of operation of said final standmotor so as to maintain the product of the thickness and velocity ofsaid issuing strip constant to the product of the thickness and velocityof said supplied strip.

2. A rolling mill as set forth in claim 1, wherein said signalcorrelating means comprises a motor having a rotor, the position of saidrotor being adjustable in response to changes in the difference betweenthe signals produced by said first and third signal generating means,and a potentiometer having a slider coupled to said rotor, said secondsignal generating means comprising a source of voltage across saidpotentiometer, the difierence in the signals generated by said first andthird signal generating means being detectable across said slider andone terminal of said potentiometer.

3. A rolling mill as set forth in claim 2, further comprising a secondpotentiometer, said first signal generating means being connected acrosssaid second potentiometer, said second potentiometer having a sliderconnected to said rotor and a high gain amplifier connected across oneterminal and said slider of said second potentiometer, the voltage dropacross one terminal and said slider of said second potentiometer beingapplied to the input of said high gain amplifier for controlling saidfinal stand motor.

References Cited in the file of this patent UNITED STATES PATENTS1,977,619 Boyer Oct. 23, 1934 2,051,018 Umansky Aug. 11, 1936 2,137,611Hetler Nov. 22, 1938 2,264,095 Mohler Nov. 25, 1941 2,275,509 DahlstromMar. 10, 1942 2,281,083 Stoltz Apr. 28, 1942 2,297,812 Stoltz Oct. 6,1942 2,303,596 Zeitlin Dec. 1, 1942 2,332,272 Shayne Oct. 19, 1943FOREIGN PATENTS 533.162 Great Britain Feb. 7. 1941

